Research on the impact of pre‐existing geological fractures on hydraulic fracturing in high in situ stress environments

Abstract The formation of complex fracture network is a difficult problem in the process of deep rock reservoir reconstruction, and the key to the generation of intricate fracture systems in deep reservoirs is to communicate more pre‐existing fractures through hydraulic fracturing, so as to enhance oil recovery. At present, there are few studies on the interactions of hydraulic fractures with pre‐existing fractures under high stress. Therefore, this research studied the influence of the number of pre‐existing fractures on the characteristics of hydraulic fractures by using advanced hydraulic fracturing instruments, and then analyzed the characteristics of hydraulic fractures under different pre‐existing fracture number based on three‐dimensional topography scanning technology and three‐dimensional square box fractal dimension calculation method. Based on the three‐dimensional finite element discrete element method, further research is carried out. The laboratory test findings indicated that the increase of pre‐existing fractures will make the pump pressure curve more stable during the test, and will significantly improve the roughness of hydraulic fractures. The numerical simulation indicated that as the quantity of pre‐existing fractures grows, the fracture area and width also increase, and in instances of a substantial quantity of pre‐existing fractures, the hydraulic fractures are prone to bifurcation, which contributes to the development of intricate fracture networks. With the increase of natural fracture angle, the fracture width decreased, but the fracture area increased. In this study, the influence of the number of pre‐existing fractures on hydraulic fracturing was studied through laboratory tests and numerical simulations, which provided theoretical reference for engineering practice.